Recently I've come up with an idea for a function:
gridFoldr :: (a -> Grid -> Grid) -> [a] -> Grid -> Grid
gridFoldr f g xs = foldr f xs g
So I can easily combine multiple grid computations using the plain (.) operator:
let grid' = gridFoldr gridOp1 args1 . gridFoldr gridOp2 args2 $ myGrid
But I have a feeling that I'm missing some general haskell concept for using a similar approach without introducing a new function. Am I right? Is there some standard function / package / or maybe some clever Monad to do the task?
It looks like you are interested in "grid updates", i.e. in functions Grid -> Grid
. This type is isomorphic to Endo Grid
, which is a well-known monoid.
So, your function is similar to
foldGrid :: (a -> Endo Grid) -> [a] -> Endo Grid
foldGrid f = mconcat . map f
or even, exploiting more libraries
foldGrid = foldMap
Indeed, foldMap
is a generalization of your function.
foldMap :: (Foldable t, Monoid m) => (a -> m) -> t a -> m